Fibrinogen is a blood coagulation factor present in the final stage of the blood coagulation cascade. When a blood vessel is damaged, the coagulation system is activated, and finally, the activated thrombin converts soluble fibrinogen into insoluble fibrin. This fibrin has adhesive strength and exerts important functions in hemostasis and wound healing.
Hemostasis and tissue adhesion operations such as tissue closure hold an important position at the medical site, especially in surgical operations, and fibrin glue adhesives to which this principle is applied are utilized in a wide range of sites of surgical operation.
Various investigations have been conducted and improvements have so far been made on methods for using a fibrin glue adhesive, and examples thereof include liquid preparations for applying or spraying a fibrinogen solution and a thrombin solution to an affected area (two-component preparations: see Japanese Examined Patent Application Publication No. H9-2971 specification and International Publication No. WO97/33633) and a method in which a sheet preparation containing fibrinogen and thrombin in mixture fixed on a support such as collagen is attached to an affected area (see Japanese Unexamined Patent Application Publication No. 2004-521115 specification).
However, in the case of the existing liquid preparations, since lyophilized fibrinogen and thrombin are dissolved separately upon use, it takes several minutes to dissolve a lyophilized preparation, and thus these preparations cannot be said to be satisfactory in terms of responsiveness to emergent surgery and convenience.
In addition, in the case of the above mentioned fibrin glue adhesives, since a higher fibrinogen concentration provides a stronger adhesive strength, a small amount of thrombin at a high concentration must be acted on fibrinogen at a high concentration.
However, in the case of the existing liquid preparations, since equal volumes of a fibrinogen solution and a thrombin solution are mixed upon use, their concentrations are reduced to 50%, preventing fibrinogen to exert its maximum efficacy. Furthermore, since the limit of fibrinogen concentration in a solution is actually about 10%, improvement in terms of concentration is difficult for a system for which two liquids are mixed in an equal volume.
In this respect, since a sheet preparation can apply a fibrinogen solution at a high concentration onto an affected site, stronger adhesive strength can be expected theoretically as compared to a two-component preparation. In addition, the sheet preparation allows astriction/compression closure at a projectile/exudative bleeding site and is expected to have excellent convenience.
When a sheet-like tissue adhesive is used, tissue penetration of the sheet preparation must be increased when applied on a wound site in order to apply a fibrinogen solution at a high concentration to the affected site. Furthermore, since a sheet preparation may be rolled or folded to closely attach to a wound site, flexibility and two-component retaining power of the sheet must be increased to prevent damage of the sheet or dropout of the fibrinogen component and thrombin component due to such force.
Sheet-like tissue adhesives and sheet-like hemostatic materials in which an active ingredient is fixed on various substrates have been disclosed (see Japanese Examined Patent Application Publication No. 61-34830 specification, Japanese Unexamined Patent Application Publication No. 2002-513645 specification, International Publication No. WO2004/064878 and International Publication No. WO2005/113030). Japanese Examined Patent Application Publication No. 61-34830 specification discloses a sheet preparation in which fibrinogen and thrombin are fixed on an equine-derived collagen surface layer and it has been put on a practice ((TachoComb (registered trademark)). However, since the collagen substrate is thick and relatively hard, adhesiveness at a wound site may decrease to make effective closure difficult. This sheet preparation has a support of equine collagen and thus, when it is to be applied to a human subject, there is a risk of development of an antibody against a heterogeneous protein and occurrence of zoonotic infections such as prion disease, and the sheet preparation cannot be said to be ideal.
International Publication of Japanese Unexamined Patent Application Publication No. 2002-513645 specification discloses a paper-like composition in which a hemostatic compound is homogenously distributed. This composition is prepared by forming a fibrous pulp comprising a bioabsorptive polymer and a hemostatic compound (mainly, thrombin, fibrinogen) in a non-aqueous solvent and subjecting the fibrous pulp to papermaking treatment. This composition reduces the time required for hemostasis by a factor of 14 as compared with TachoComb and enables re-attachment. However, since it has a paper-like shape, there is a room for improving tissue-following property.
International Publication No. WO2004/064878 and International Publication No. WO2005/113030 disclose a material using a sheet in which thrombin is fixed on a bioabsorptive synthetic non-woven fabric and a fibrinogen solution in combination. For these compositions, a non-woven fabric is immersed in an aqueous solution of an active ingredient followed by lyophilization to make a composite. This method suffers from problems such as a low yield of the lyophilization step, low flexibility of the sheet, and poor supporting characteristic for fixed protein to lead to peeling-off from the sheet.
Japanese Unexamined Patent Application Publication No. 2009-183649 specification discloses a sheet-like tissue hemostatic material comprising a fibrinogen-containing layer and a thrombin-containing layer provided therebetween with an intermediate layer containing a cellulose derivative as a material; however, there are such problems that the solubility of fibrinogen contained in the tissue hemostatic is insufficient and the handling property is poor and cannot be trimmed since it is a lyophilized product.
In addition, as sheet preparations, Japanese Unexamined Patent Application Publication No. 2010-069031 specification discloses a sheet-like fibrin glue adhesive comprising a bioabsorptive support on which fibrinogen containing a non-ionic surfactant is fixed and a bioabsorptive support on which thrombin is fixed; Japanese Unexamined Patent Application Publication No. 2002-515300 specification discloses a sandwich bandage for hemostasis comprising a fibrinogen layer, a thrombin layer, an absorption material layer and the like; and Japanese Unexamined Patent Application Publication No. 2009-533135 specification discloses a porous wound care product comprising a first absorptive non-woven fabric, and at least one second absorptive woven fabric or knitted fabric, and thrombin and/or fibrinogen. However, since these hemostatic materials are manufactured by lyophilization of fibrinogen and thrombin, fibrinogen and thrombin readily drop off, the material is insufficiently flexible, and the tissue adhesion effect described above is insufficient because fibrinogen and thrombin are present adjacently to each other. In addition, when a preparation is in the form in which fibrinogen and thrombin are in direct contact to each other, coagulation reaction proceeds to form fibrin even with a trace amount of water during storage, causing a problem in storage stability. Further, there was also a problem of requiring vast amounts of time and labor for manufacturing due to the necessity of a lyophilization step.
No sheet-like hemostatic material for which effect and convenience can be expected actually has been established by the combination of fibrinogen and thrombin as described above. Further, although a fibrinogen solution at a high concentration is required to exert a strong tissue adhesion effect, since fibrinogen is poorly soluble, fibrinogen is scarcely dissolved when fibrinogen is fixed on a support while retaining a conventional composition due to poor solubility of fibrinogen and thus sufficient drug efficacy cannot be expected to be exerted.